Start of 'namespace' blob storage target.

Change-Id: I7b6f1a9eea1a7b37482e890238dabc9f1a39c4a5

pkg/blobserver/namespace/ns.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2014 The Camlistore Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package namespace implements the "namespace" blobserver storage type.
+//
+// A namespace storage is backed by another storage target but only
+// has access and visibility to a subset of the blobs which have been
+// uploaded through this namespace. The list of accessible blobs are
+// stored in the provided "inventory" sorted key/value target.
+package namespace
+
+import (
+	"fmt"
+
+	"camlistore.org/pkg/blobserver"
+	"camlistore.org/pkg/jsonconfig"
+	"camlistore.org/pkg/sorted"
+)
+
+type nsto struct {
+	inventory sorted.KeyValue
+	master    blobserver.Storage
+
+	blobserver.NoImplStorage // TODO(bradfitz): remove this and finish implementing
+}
+
+func init() {
+	blobserver.RegisterStorageConstructor("namespace", blobserver.StorageConstructor(newFromConfig))
+}
+
+func newFromConfig(ld blobserver.Loader, config jsonconfig.Obj) (storage blobserver.Storage, err error) {
+	sto := &nsto{}
+	invConf := config.RequiredObject("inventory")
+	masterName := config.RequiredString("storage")
+	if err := config.Validate(); err != nil {
+		return nil, err
+	}
+	sto.inventory, err = sorted.NewKeyValue(invConf)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid 'inventory' configuration: %v", err)
+	}
+	sto.master, err = ld.GetStorage(masterName)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid 'storage' configuration: %v", err)
+	}
+	return sto, nil
+}